Coil insulating and lead anchoring means for transformers



1951 A. F. MITTERMAIER ETAL 3,011,140

COIL INSULATING AND LEAD ANCHORING MEANS FOR TRANSFORMERS Filed Aug. 1, 1960 United States Patent Cfiice a 011 140 COIL INSULATING ANi) LEAD ANCHORING MEANS FOR TRANSFORMERS Armin F. Mittermaier, Fort Wayne, and Albert F. Wilcox, Yoder, Ind., assignors to General Electric Company, a corporation of New York Filed Aug. 1, 1960, Ser. No. 46,487 12 Claims. (Cl. 336-198) This invention relates to core and coil assemblies and more particularly to improved means for insulating a coil and anchoring conductors and for anchoring coil leads.

The need for adequate insulation between the outer corners of the coil and the inside corners of the core has long been recognized in the art. However, the problem of providing such insulation of a coil from the core has been difiicult to solve economically. Prior constructions in which transformer coils were provided with insulation between the inner corners of the core and the outer corners of the coil have not been satisfactory because the constructions were not readily adaptable to automatic and semiautomatic assembly techniques.

Although the outer surface of the coil is generally provided with an insulating wrapper, arcing may still occur between the outer corner of the coil and the inner corner of the core; The coil creepage may cause the coil wire at the corner of coils to come in contact with the core. Arcing may take place because the outside insulating wrapper of the coil does not completely cover the corners of the coil. I I

Triangular paper flaps formed on a coil bobbin, such as are described in US. Patent No. 2,5 1l,174-'-Osborne, have been used to insulate the outer edges of a coil from the inner corners of the coil. However, this arrangement has not been entirely satisfactory from a manufacturing cost standpoint since a separate assembly step: isrequired to fold over the insulating tabs. Moreover, the bobbin does not possess the desired rigidity, and no convenient means is provided for bringing out anchoring or insulating the coil conductors.

' In many prior art constructions it has been necessary 1 to provide start and finish insulation for coil conductors in order to efiectively insulate the coil conductors from the core. Although such insulation has proven to be effective, it has not been satisfactory where it is desired to keep manufacturing costs at a minimum. The elimination of the need for insulation on the coil conductors results in an overall reduction in manufacturing costs. Further, it is desirable that some means be provided for anchoring the conductor leads of the coil so that the leads are properly positioned for attachment to external leads and can be readily connected to external leads.

Accordingly, an object of this invention is to provide an improved core and coil assembly which incorporates the desirable features described above.

It is a more specific object of the invention to provide an arrangement of core and coil assembly in which the corners of the coils and coil conductors will be effectively insulated from the core.

Another object of this invention is to provide an improved means for effectively anchoring and positioning coil leads brought out from a coil.

It is still a further object of this invention to provide an improved arrangement of a core and coil assembly that is readily adaptable to automatic and semiautomatic as sembly methods.

In accordance with the invention we have provided a core andcoil assembly having a center winding leg member and a pair of outer leg members formed of superposed laminations in which an electrical coil wound on a bobbin is disposed on the center winding leg member. The

bobbin has a substantially rigid flanged element at each end extending substantially perpendicular to the plane, of i over the sides of the coil as the coil bobbin is assembled on the center winding leg member andthe insulating flaps engage the outer leg members.

"In another aspect of the invention, the coil bobbin is provided with a slot extending radially of the flanged element and with an insulating tab formed integrally with the flanged element and extending outwardly thereof from a line at the base of the slot and substantially perpendicular thereto to provide an insulating barrier for thecoil conductors. A rounded lip projection is formed on the flanged element and integrally therewith where the center winding leg member enters the coil bobbin and along a line parallel to the insulating tab to facilitate entry of the center winding leg member into the aperture of the coil bobbin and also to reinforce the bobbin spool.

The subject matter which we regard as our invention is set forth in the appended claims. The invention itself, however, together with further objects and advantages thereof may be better understood by referring to the following description taken in connection with the accompanying drawings in which: 7

FIG. 1 is a view in perspective of a transformer coil and core assembly illustrating a preferred embodiment of the invention;

FIG. 2 is an exploded view in perspective of the coil assembly and magnetic core lamination stacks of the transformer of FIG. 1 illustrating how the insulating flaps are folded over as the magnetic core is assembled;

FIG. 3 is a partially sectionalized front elevation of the transformer core and coil assembly of FIG. 1;

FIG. 4 is a fragmentary elevation of a transformer core and coil assembly of FIG. 1; and

FIG. 5 is a side elevation of the coil bobbin used in the transformer core and coil assembly of FlG. 1;

-Referring now to FIGS. 1-4, there is shown a transformer core and coil assembly 11 comprising a pair of stacks 12, 13 of E-shaped laminations and an electrical coil assembly 1'4. The lamination stacks 12, 13 are butted against each other to form a magnetic core 16 defining a closed magnetic circuit. As shown in FIG. 3, the magnetic core 16 is comprised of a pair of outer core leg members 17, 18, a center winding leg member 19 and a pair of transverse members 21, 22. All of the laminations lying in a given stack are similar to all the other laminations lying in the same stack with the corresponding legs of all E-shaped laminations in the same stack being of [the same length. The center legs 23, 2'4 of the respective lamination stacks 12, 13 may be made shorter than the outer legs to provide a predetermined air gap 26 in the winding leg member 19 for control of the magnetizing reactance of the core and coil assembly 11. Although the magnetic core 16, as shown in FIG. 4, is made up of two stacks of E-shaped laminations, it will be appreciated that the core of the structure can also be made up of a stack of E-shaped laminations and a stack of l-shaped laminations butted against each other to form a closed magnetic circuit.

The electrical coil assembly 14 is positioned on the center winding member 19. In order to hold lamination stacks 12, 13 and the coil assembly 14 tightly in assembled relation and also to provide a suitable mounting means, the core supporting clamps 2.7, 28 are provided. The core supporting clamp arrangement is. fully described and claimed in thecopending application Serial No. 45,3 68, filed on July 26, 1960, in the name of Armin Paten ed Nov. 28, 1961 u F. Mittermaier and assigned to the same assignee as the present invention. 7

Referring to FIG. 3, it will be seen that the coil assembly 14 is comprised of a coil bobbin 29, a winding and an insulating wrapper 31. In the illustrative embodiment of the invention, the winding 30 was an autotransformer winding connected to the external leads 32, 3'3, 34. The coil bobbin 29 in accordance with the invention is integrally formed of a resilient insulating material, such as nylon. As shown in FIGS. 2 and 5, the bobbin 29 has a pair of flanges 36, 37 which form a spool portion for the winding 30 and also insulate the winding 30 from the magnetic core 16. A pair of slots 38, 39 are provided to permit leads to be brought out from the winding. At the base of the slots 38, 39 and extending across the winding =leg receiving aperture 41 of the bobbin 29, insulating tabs 42, 43 are provided as an insulation barrier to prevent arcing between a coil lead 44 and the magnetic core 16. Further, the insulating tabs 42, 43 serve the purpose of facilitating entry of the center Winding legs 23, 24 into assembled relation within the aperture 41 of the bobbin 29. This results in the advantage that the coil bobbin 29 can be assembled readily on winding legs of varying stack heights. It will be appreciated that although stacks of laminations may have the same number of laminations, it is difficult to maintain a constant stack height because the laminations are not true planar surfaces and because of slight variations in the thickness of the individual laminations. Although the width of the center Winding legs 23, 24 can be effectively controlled, the stacking height cannot be precisely controlled in a manufacturing operation. Consequently, the insulating tabs 42, 43 serve as a shoe-horn for effecting snug fit between the center winding legs 23, 24 and the coil bobbin 29. \As a consequence, a diminution of the noise level of the magnetic core 16 is achieved.

To further facilitate entry of the center winding legs 23, 24 rounded lip projections 46, 47 are formed at each side opposite from the insulating tabs 42, 43. Thus, the insulating tabs 42, 43 and the rounded lip projections 46, 47 cooperate to effect the entry of the center winding legs 23, 24. Further, the insulating tabs 42, 43 and the rounded lip projections 46, 47 also provide advantage in that they also serve as reinforcing ribs for the flange elements 36, 37 of the bobbin 2% and provide the bobbin 29 with additional rigidity.

The outer edges of the flanged elements 36, 37 of the bobbin 29 are formed with notches 49a, 49b, 49c, 49d and 50a, 50b, 50c, 50d for positioning external leads and also for a minimizing of the effect of tension that might be applied to the external leads. Coil lead anchor pins 51, 52, 53 are provided at proximate locations to the coil slots 38, 39 so that coil leads, such as the coil lead 44 can be anchored. Additional pins may be provided as required.

In the exemplification of the invention as shown in FIG. 2, four flexible insulating flaps 54, 55, 56, 57 integrally formed with the flanges 36, 37 are provided for the purpose of insulating the edges of the coil winding 30 from the corners of the magnetic core 16. As shown in the exploded view of FIG. 2, as the stacks 12, 13 of E-shaped laminations are inserted into the aperture 41 of the bobbin 29, the flaps 54, 55, 56, 57 fold over the coil and effectively insulate the corners. It will be appreciated that the corners are eifectively insulated simultaneously with the assembly of the coil bobbin 29 on the magnetic core 16. Thus, it is seen that a separate step in the manufacturing operation is not required to achieve corner insulation.

Referring now particularly to FIG. 2, it will be seen that the insulating flaps 54, 55, 56, 57 have a thickness less than the thicknes of the flanged elements 36, 37 and are sufliciently thin to permit the flaps to fold over around the corners of the coil winding 30 as they engage the magnetic core 16 during assembly. Prior to assembly the insulating flaps 54, 55, 56, 57 are unfolded so that the core assembly 14 can be readily wound without inter ference from the flaps 54, 55, 56, 5'7. It will, of course, be understood that if desired, the length of the flaps may be further extended along the sides of the core assembly 14 to completely insulate the coil sides. Thus, in accordance with the invention the bobbin is a unitary structure providing positive insulation barriers at all of the critical points of the core and coil assembly 11. The same unitary structure also provides an anchoring and positioning means for the external leads and also for the coil leads brought out from the coil winding.

While we have described above a particular embodiment of the invention, many modifications may be made. it is to be understood, therefore, that we intend by the appended claims to cover all such modifications that fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

l. A magnetic coil and core assembly comprising a magnetic core formed of a plurality of superposed laminations of magnetic material, said magnetic core having a center winding leg member, a pair of outer leg members respectively disposed on opposite sides of said center winding leg member, and a pair of transverse members joining said outer leg members with said center winding leg member, a coil bobbin mounted on said center winding leg member and having a substantially rigid flanged element formed at each end of the bobbin extending substantially perpendicular to the plane of said laminations and defining a spool portion, an electrical coil disposed within said spool portion, said flanged elements insulating the ends of said coil from said transverse members of said magnetic core adjacent thereto, an insulating flap integrally formed with said flanged element at each edge thereof adjacent to said outer leg members, and having a thickness less than the thickness of said flanged element and being sufiiciently flexible to permit said flap to fold over the sides of said coil when assembled on said center winding leg member, said insulating flaps insulating at least the corners of said coil adjacent to said outer leg members from said magnetic core.

2. A magnetic core and coil assembly comprising a core formed of a plurality of superposed laminations of flat stacked magnetic material, said magnetic core having a center winding leg member, a pair of outer leg members respectively disposed on opposite sides of said center winding leg member and a pair of transverse members joining said outer leg members with said center winding leg member and forming therewith a magnetic flux return path between the ends of said center Winding leg members, a coil bobbin having a substantially rigid flanged element disposed at each end of said bobbin extending substantially perpendicular to the plane of said laminations and defining a spool portion, an electrical coil disposed within said spool portion and having at least one coil lead extending therefrom, said flanged elements insulating the ends from said transverse members of said magnetic core adjacent thereto, one of said flanged elements being formed with a slot extending radially therefrom and said coil lead being brought through said slot for connection with an external lead, an insulating tab formed integrally with said flanged element and extending outwardly from a line thereon substantially perpendicular to said slot to provide insulation between said coil lead and the laminations of said adjacent transverse member, and an insulating flap formed integrally with each edge of said flanged element adjacent to said outer leg members of said magnetic core, and having a thickness less than the thickness of said flanged element and being sufliciently flexible to permit said flap to fold over the sides of said coil when assembled on said center winding leg member.

3. The magnetic core and coil assembly set forth in claim 2 wherein a lip projection is formed along said flanged element and integrally therewith where said center leg member enters said coil bobbin and along a line parallel to said insulating tab to facilitate assembly of said magnetic core on said coil bobbin and to reinforce said flanged element.

4. The magnetic core and coil assembly set forth in claim 2 wherein a means for engaging external leads is provided on said flanged element of said coil bobbin proximate to said slot.

5. A magnetic core and coil assembly comprising a pair of E-shaped lamination stacks joined together to form a closed magnetic core, each of the legs of said stacks of E-shaped laminations being respectively aligned with the legs of the other stack to form a magnetic core having two outer leg members, a pair of transverse members and a center winding leg member, a coil bobbin mounted on said center winding leg member and having a flanged element disposed at each end thereof substantially perpendicular to the plane of said laminations and defining a spool portion, an electrical coil disposed within said spool portion, an insulating flap integrally formed with said flanged element at each edge thereof adjacent to said outer leg members, and having a thickness less than the thickness of said flanged element and being sufliciently flexible to permit said flap to fold over the sides of said coil when assembled on said center winding leg member.

6. A magnetic core and coil assembly comprising a pair of E-shaped lamination stacks joined together to form a closed magnetic circuit, each of the'legs of said stacks of E-shaped laminations being respectively aligned with the legs of the other stack to form a magnetic core having two outer leg members, a pair of transverse members and a center winding leg member, a coil bobbin mounted on said center winding leg member and having a flanged element disposed at each end thereof substantially perpendicular to the plane of said laminations and defining a spool portion, an electrical coil disposed with said spool portion and having at least one coil lead extending therefrom, said flanged elements insulating the ends of said coil from said transverse membersof said magnetic core adjacent thereto, one of said flanged elements being formed with a slot extending radially therefrom and said coil lead being brought through said slot for connection with an external lead, an insulating tab formed integrally with said flanged element and extending outwardly from a line thereon substantially perpendicular to said slot to provide insulation between said coil lead and the laminations of said magnetic core, and an insulating flap formed integrally with each edge of said flanged element adjacent to said outer leg members of said magnetic core, and having a thickness less than the thickness of said flanged element and being sufliciently flexible to permit said flap to fold over the sides of said coil when assembled on said center winding leg member. s

7. The magnetic core and coil assembly set forth in claim 6 wherein an arcuate projection is formed along said flanged element extending outwardly thereof from a line on said flanged element substantially parallel to said insulating tab to cooperate with said tab to facilitate 6 assembly of said coil bobbin on the winding leg of said magnetic core.

8. The magnetic core and coil assembly set forth in claim 6 wherein a means for engaging an external lead is provided on said flanged element of said coil bobbin.

9. A coil bobbin comprising a winding leg receiving portion having an aperture adapted for mounting on the Winding leg of a magnetic core and having a central axis, a substantially rigid flanged element extending vertically ofsaid axis from each end of said winding leg receiving portion and defining a spool portion, a pair of insulating flaps oppositely disposed on said flanged element and extending outwardly thereof in the plane of said flanged element and having a thickness less than the thickness of said flanged element and being sufliciently flexible to permit said flap to fold over the sides of said coil when assembled on said winding leg member.

10. A coil bobbin comprising a quadrilaterally shaped winding leg receiving portion, a substantially rigid flanged element extending vertically outward at each end of said winding leg receiving portion to define a spool portion, said flanged elements having a substantiallyquadrilateral configuration, said edges of said flanged elements being I substantially parallel to the sides of said winding leg member receiving portion, the opposite edges of each of said flanged portions having formed integrally therewith insulating flaps extending outwardly therefrom, said insulating flaps being readily foldable to form an insulating barrier for at least a part of a coil disposed within said spool portion.

11. A coil bobbin and electrical coil assembly comprising a winding leg receiving portion having an aperture adapted for mounting on the winding leg of a mag netic core and having a central axis, a flanged element extending vertically of said axis from each end of said winding leg receiving portion and defining a spool portion, said flanged element having aslot extending radially therefrom, an electrical coil disposed within said spool portion and having at least one lead extending through said slot, an insulating tab formed integrally with said flanged element and extending outwardly from a line thereon substantially perpendicular to said slot to insulate said coil lead from adjacent core parts and a pair of insulating flaps oppositely disposed on said flanged element and extending outwardly thereof in the plane of said flanged element, said insulating flaps being foldable when assembled on a magnetic core and having a thickness less than the thickness of said flanged element and being sufliciently flexible to permit said flap to fold over the sides of said coil when assembled on said center winding leg member. s

12; The coil bobbin and electrical coil assembly set forth in claim 11 wherein an arcuate projection is formed along said flanged element extending outwardly thereof froma line on said flanged element substantially parallel to said insulating tab to cooperate with said insulating tab to facilitate assembly of said coil bobbin on the winding leg of said magnetic core.

No references cited. 

